package com.ideaaedi.commonds.chars;

import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;

/**
 * util for char
 *
 * @author <font size = "20" color = "#3CAA3C"><a href="https://gitee.com/JustryDeng">JustryDeng</a></font> <img src="https://gitee.com/JustryDeng/shared-files/raw/master/JustryDeng/avatar.jpg" />
 * @since 1.0.0
 */
public class CharUtil {
    
    public static final Character[] CHAR_POOL = {
            '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
            'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
            'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
            'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
            '!', '@', '#', '$', '%', '^', '&', '*', '(', ')', '-', '=', '_', '+', '.'
    };
    
    /**
     * 生成指定长度的随机字符串
     *
     * @param length
     *            长度
     * @return  字符数组
     */
    public static char[] generateCharArr(Character[] chars, int length) {
        if (chars == null || chars.length == 0) {
            throw new IllegalArgumentException("char cannot be empty.");
        }
        char[] result = new char[length];
        List<Character> list = Arrays.asList(chars);
        // "洗牌"
        Collections.shuffle(list);
        Random random = new SecureRandom();
        for (int i = 0; i < length; i++) {
            if (i < chars.length) {
                result[i] = list.get(i);
            } else {
                result[i] = list.get(random.nextInt(chars.length));
            }
        }
        return result;
    }
    
    /**
     * 生成指定长度的随机字符串
     *
     * @see CharUtil#generateCharArr(Character[], int)
     */
    public static char[] generateCharArr(int length) {
        return generateCharArr(CHAR_POOL, length);
    }
}
